Cassette Review: Shimano XTR, XT and Sram 990, 980, 970, 950

Pictures and reviews of mountain bike cassettes including Shimano XTR Cassette, Shimano XT Cassette and Sram 990 (red alloy spider), 990 (old style), 980, 970, 950.

The problem: mountain bike cassettes that chew up or get stuck on a freehub. The images below show a free hub that was used for 250 miles with a Sram PG 980 cassette followed by about 800 miles with a Sram PG 970. The Sram PG 980 cassette was removed because freehub damage was noticed after only 250 miles. It was replaced with a Sram PG 970 which after about 700 miles had become stuck on the freehub body. With some careful pounding, pushing, and prying, we removed the stuck cassette from the freehub body and filed down the burrs on the freehub. We put the Sram PG 970 back on for another 100 miles and it came off easily but still had created some burrs that needed filing. While the freehub is still useable, we feel that the damage seen is unnecessary and due to poorly designed Sram cassettes. Furthermore, we recommend only cassettes with solid smooth spiders such as the Shimano XTR, Shimano XT or Sram PG 990.

The best cassettes that are easy on the freehub seem to be ones with a solid smooth spider where only the top 3 rings are removeable from the spider.

The cassettes we liked the best were in order

Shimano XTR CS-M960
Shimano XT CS-M760
Sram PG990 (either red alloy or prior model)

The cassettes we would recommend against using as they seem to be prone to damage the freehub body are

Sram PG980
Sram PG970
Sram PG950

The most durable of the cassettes that we like seem to be the Shimano XTR with the Sram PG 990 being the least durable and slightly heavier than the more affordable Shimano XT model. The older Sram 990 seems to be even less durable than the 2006 PG 990 with the red allow spider.

Individual Mountain Bike Cassette Reviews

Shimano XTR CS-M960 Cassette
The Shimano XTR CS-M960 is our favorite 9 speed mountain bike cassette. The XTR cassette is the lightest available of the cassettes tested, the most expensive at about $160 and the largest 4 cogs are made of titanium. The XTR cassette has a very nicely finished smooth alloy spider and held up to the abuse we dished out on it.

Shimano XT CS-M760 Cassette
The XT cassette is heavier than the XTR, although still one of the lightest available. It generally is about $100 cheaper than the XTR model usually costing about $70 and does not contain any of the titanium of the XTR cassette. The XT cassette still has a nice smooth solid spider however and would be less likely to damage the freehub than the many Sram models available.

Sram PG 990 Cassette, 2006 with Red Alloy Spider
The Sram PG 990 cassette is heavier than the Shimano XT model and Sram's top of the line mountain bike cassette. The Sram PG 990 can be found for about $100. The Sram PG990 with the red spider is a nice looking cassette and definately will add some color to the bike. The spider is also nice and smooth and should be easy on the freehub body.

Sram PG 990 Cassette, 2005 model
The Sram PG 990 cassette 2005 model is a nice light cassette with a good smooth spider for good freehub contact. As of this writing 12/06, it can still be found for around $60 online from places that seem to have an overstock of the item and cannot sell out. We found that this cassette wore out rather quickly, it seemed softer than some of the other cassettes. As flimsly as it looks, it actually was quite sturdy on the bike and we did not experience any problems with bending it in any way.

Sram PG 980 Cassette
The Sram PG 980 cassette is hard to find and we highly recommend against using this cassette. The problem with this cassette is that the lower 6 cogs of the cassette, which on all the other cassettes is one solid piece, are split into 2 pieces. We feel that this just creates unnecessary pressure on the freehub body as it does not allow the torque load to spread over the entire freehub body and will quickly lead to damage of the freehub.

Sram PG 970 Cassette
The Sram PG 970 cassette is Sram's middle-of the pack cassette. In our opinion this cassette, along with the PG 950 has a very poor design at the contact of the freehub body. The cassette alternates between steel cogs and plastic spacers instead of having a true spider. This puts all of the torque on the small area of metal of the cogs contacting the freehub body and will cause the cassette to dig into the freehub body. This cassette is not cheap, usually around $50 and is quite hefty. We apologize for the dirt.

Sram PG 950 Cassette
The Sram PG 950 cassette is Sram's entry level cassette. As with the PG 970, this cassette has a great potential to damage the freehub because the torque forces are focused on small contact points of metal to metal rather than spread out over and entire smooth spider. We recommend against using this cassette.